Sea-stars are Echinoderms. The order Ophiuroides is closely related to starfishes. The arms of sea stars however, differ from those of starfishes in not containing any prolongations from the stomach.
GalleriesSea Urchins and Sea Stars
H. Alleyne Nicholson, An Introductory Text-book of Zoology(Edinburgh:William Blackwood and Sons, 1971) 54